The delays at TIA are tough to predict, and generally stem from three causes:

If your destination or departure is in the northeastern United States, a delay is possible. If you change planes anywhere along the eastern seaboard, brace for a possible delay.

And if you're unlucky enough that your plane has to pass through the Atlantic Coast just to get to you -- even if you're not flying there -- you may get stuck with a delay.

"This shouldn't go down as being one of the historical monster storms, especially since temperatures are warm enough to keep snow away from the main airports," says Brett Snyder, founder and president ofCranky Conciergeair travel assistance.

"It's just that the timing is so bad, hitting on one of the busiest travel days of the year," adds Snyder, who also authors the highly-regarded Cranky Flier blog.

In addition to its Thanksgiving-eve arrival, the storm also will hit some of the nation's busiest and most delay-prone airports. Among the those in the storm's path are New York LaGuardia, Newark Liberty and Philadelphia - each of which can suffer significant disruptions even during moderate weather events.

"New York City and Philadelphia seem to be where the brunt of the storm will be" for air travel, Daniel Baker, CEO of the flight-tracking serviceFlightAware, says in an e-mail to Today in the Sky. "But I think D.C. might also be impacted and that's notable because United has a big hub at Dulles."

Besides Dulles, United -- the nation's biggest carrier -- also has a hub at Newark Liberty. In fact, nearly every big U.S. airline has a hub at one of the cities likely to be affected by the storm: In Philadelphia, it's US Airways, while New York JFK - another delay-prone airfield in the storm's path - is a hub for three big airlines: American, Delta and JetBlue.

Anticipating potential problems, more than a half-dozen carriers - including the USA's three biggest - had waived fees for some customers ticked to fly to airports threatened by the storm.

But fliers in other parts of the nation should be wary, as well.

"If there are a large number of cancellations on the East Coast then that could impact flights elsewhere in the country," says Snyder.

He cites an example of a New York-to-Phoenix flight that may be scheduled to continue on to another destination - perhaps San Diego.

"If that airplane gets stuck in New York, then there could be an issue for those flying just between Phoenix and San Diego," Snyder says, which. "The biggest problem is that because of the holiday, flights are extremely full. So there won't be easy re-accommodation options" for other flights.

"The airlines are hoping to take a lot of delays rather than cancellations tomorrow," he says about Wednesday's flight schedules. Because of that, Baker says "it's likely that travelers even on the West coast could be impacted."

As for Tuesday's operations, delays were a problem at some busy airports - though there were few major problems. FlightAware counted just over 125 cancellations as of 6 p.m. ET, a relatively small number given that a major storm was moving across the nation.

But delays were a problem at a handful of airports, according to FlightAware's Baker. Atlanta - the world's busiest - suffered "hundreds" of delay flights on Tuesday, "but it will likely be unaffected (Wednesday) when the storm hits the Northeast," Baker says.

Data from FlightStats, another flight-tracking firm, backed up the scope of Tuesday's delays. At Atlanta, FlightStats says about 1 in 3 flights suffered some sort of delay through 5 p.m. ET on Tuesday. As for airlines, more than 1,000 of Southwest's flights -- about a third of its daily total -- had been delayed,according to FlightStats.

As bad as that sounds, Snyder suggest that those in their cars may end up in even worse shape on Wednesday -- at least in the Northeast.

"At this point, it looks like drivers may see the biggest problems," Snyder says. "The biggest impact will be on drivers that are west of the main east coast cities. There could be some difficult travel conditions."